Process of controlling the sulphur-dioxide content of dried fruit



1929- F. J. PROWSE ET AL 1,724,514

PROCESS OF CONTROLLING THE SULPHUR DIOXIDE CONTENT OF DRIED FRUIT .l l lV Patented Aug. 13, 1929. I

UNITED STATES.

PATENT OFFICE.v

FRANCIS J. PBOWSE, OF SAN JOSE, RAYMOND D. ROBINSON, OF D, ERNEST MI.HALL, OF FRESNO, AND CHARLES F. FLEMING, OF SAN JOSE, CALIFORNIA, AS-

SIGNORS TO CALIFORNIA PACKING'CORPOBATION, OF SAN NIA, A CORPORATION OFNEW YORK.

FRANCISCO, CALIFOR- PROCESS OF CONTROLLING THE SULPHUR-DIOXIDE CONTENTOF DRIED FRUIT.

Application filed my a,

' This invention relates to a process of controlling the sulphur dioxidecontent of dried fruits, such as dried peaches, apricots, prunes,raisins, or other fruits which are treated with sulphur fumes.

In the preparation of dried fruits, of the kinds to which this inventionparticularly relates, the fruit is sulphured in the first instance bythe grower. This is customarily accomplished by subjecting the fruit fora period of time to sulphur dioxide fumes.

" The length of time that the fruit is exposed to the sulphur dioxideatmosphere, as well as the strength of the sulphur dioxide atmosphere,and the character of the fruit, determines the extent to which the fruitis impregnated with sulphur dioxide. The object of the sulphuring of thefruit is to prevent a subsequent darkening of the fruit and to keepgoinsects away from the same during the sundrying which follows. Afterthe fruit is sulphured and dried, it is forwarded by the grower to apacking-house, where it is stored for a period of time before beingpacked for market. There is. no uniform practice among growers as to thelength of time that the fruit is exposed to the sulphur dioxideatmosphere, and this,tog.ether with the varying character of the fruitand the fact that the different growers do not employ the same strengthof sulphur-dioxide atmosphere, re- I sults in the treated fruit beingreceived at the packing-house with varying degrees of sulphur dioxideimpregnation. Much of this. treated fruit arrives at the packing-housewith'a larger sulphur dioxide content thanis desired by the trade ortolerated by law. During the time the treated fruit is stored atthpacking-house, the fruit continues to dry, and when desired for ackinghas become so hard and tough as to e diflicult to prepare into an edibleproduct. To prepare the treated fruit for packingfthe fruit is cleanedand passed through what is known as a processor, in which the fruit iscontinuously washed with water. -Durin this washing process, suflicientwater is a sorbed by the fruit to make it more edible. The fruit is thenput into a sulphur-house and is re-sulphured. Different fruits respondmore or less rapidly to treatment with sulphur dioxide, and the sulphurdioxide content of 1925. Serial No. 28,358.

the dried fruit being irregular, as has been heretofore explained, itresults that with prior methods of handling the fruit leaves thepacking-house for the consumer impregnated w1th widely varying andexcessive amounts of sulphur dioxide.

Our' invention has for its object controlling the sulphur content of thedried fruit to meet therequirements of the trade and the regulationsimposed by law, which are to some extent exceeded in fruit handled inaccordance with the prior practice. It has been the accepted theory thatthe color stability and keeping quality of the fruit is largelydependent upon the sulphur dioxide content of the fruit and that it isnecessary at the t me of softening and preparing the previouslysulphured dried fruit for market to further sulphur the fruit. We havefound that the fruit may or may not need to be further sulphured at thetime of softening in preparation for market, provided the softened fruitbe maintained over a period of time at a proper temperature and in thepresence of air or other atmosphere. Although proceeding in accordancewith our invention unobjectionable sulphur bodies. We control theextraction and conversion of sulphur dioxide so that the sulphur dioxideremaining in the fruit 'is snflicient to maintain the color stabilityand keeping quality of the fruit and yet permit a reduction of thesulphur diox-' ide content of thefruie to within the prescribed limits.By regulatitng the time and conditions of our treatment, we are able toso control the-residual sulphur dioxide content of the fruit withingreater or lesser limits,

and-can thus closely prescribe the ultimate sulphur dioxide content ofthe fruit, accomlishing a result that has long been sought or but neverheretofore attained.

The conditions of our process must be vafruit as received from thegrower, and our ina and description, we will describe b by which thefruit isrwetted.

. subjecting t vention is not limited in application to any particularform of apparatus for performing the process. In the accompanyingdrawings way of example an operation embodying this process and theapparatus by which the same has been successfully practiced underconditions of actual use. p In the accompanying diagrammatic drawmgsFigure 1 is a plan view of the apparatus Figure 2 is a detailedside-view of theriflles .embodied'in 1 and showing the direction ofapplication of the water-spray employed for wetting the fruit.

Figure 3 is a side-elevation partly in section showing the apparatusemployed for e wetted fruit to the sulphur dioxide controllingatmosphere.

Referring to the drawings when it is desired to prepare and pack thedried sulphurtreated fruit that has been received from the grower, thefruit is delivered tov a shaker 2 provided with a plurality of rifiles 3and screens 4:. Water is directed upon the fruit at an angle by means ofsprays 5. The wetted fruit is passed to a tray 6, upon which tray thefruit is spread. vThe ob ect of'wetting the fruit upon the apparatuslast described is to soften the'fruit and render it susceptible to theaction of thesulphur dioxide controlling atmosphere to which it is next.to be subjected. The trays of wetted fruit 6 are then placed within asulphur-controlling room or chamber 7 having a door 8. The specificarrangement illustrated in Fig. 3 of the drawmgs embodies a circulatingfan -9 for circu ating a sulphur-controlling atmosphere through and overthe fruit on the trays-6.

A heating coil 10 may be provided to heat the room or chamber 7. A pan11 is pro- 1 vided for burning sulphur if desired to prosulphur dioxideby the grower. Under cer-' .tain conditions it will befound vide asulphur atmosphere in the room or chamber 7. W K r It must be understoodthat-the conditions under which the process isoperated to control theultimate sulphur dioxide content'of the fruit mustv vary withldiflerentgrades of fruit, and in accordance with the extent to WhlCh the fruithas been impregnated with vantageous to s ray the fruit at 5 with heatedwater to ren er more efiective-the softening of the fruit. It" is alsocontemplated. that under certain conditions'the wetted fruit may bemaintained for a period of time in the chamher or room 7 at'an elevatedtemperature to further soften the fruit. The wetted or softenedsulphured fruit is then maintained in Mattie the chamber 7 for a periodof'time during which a su hur dioxide controlling atmosphere iscirculated through or over the fruit.\ This sul hur dioxide controllingatmosphere will preierably be natural air, although other substituteswill naturally occur to those employing the invention, and'anyatmosphere fruit is maintained under the influence of the .sulphurdioxide controlling atmosphere varies in accordance with the characterof the fruit, and with the amount of original sulphur dioxide contentthereof, and the maximum sulphur dioxide content to be left impregnatedin the fruit. The action of the sulphur dioxide controlling atmosphereis to liberate a portion of the original sulphur dioxide content (SO ofthe softened fruit and dioxide content. of the fruit into other sulphurbodies. By regulating the conditions of the operation in accordance withthe character of the fruit being handled and the origito convert aportion of the remaining sulphurnal sulphur dioxide content of thefruit, the

residual sulphur dioxide content of the fruit may be controlled withinthe prescribed limitsdesired. After the sulphur dioxide content of thefruit has been'brought-within the desired limits the extraction andconversion of the sulphur dioxide content of the softened fruit by andthe fruit redried.

In view of the varying conditions under which our .process may beerformed, we shall now set forth by way 0 example these conditions for asuccessful operation as actually practiced by us employing the appara;tus diagrammatically illustrated in the acc'ompanying drawings. Peacheswhich have been sulphured by the grower and stored until too hard andtough to bef-edible, were wetted on the shaker 2' by water having atemperature of approximately 165 to 170 F. Immediately uppn receipt ofthe wetted fruitfrom the shak 2 the same was spread upon tray 6 andconveyed tothe sulphur-- econtrolling room or chamber 7. The sulphurdioxide content than was ultimately desired for the fruit at the end ofthe sweating period a sulphur-dioxide controlling atmosphere (moist air)was circulated through the the circulation of'air is discontinued fruitby means of the fan 9. No time limit maybe prescribed for continuing thecirculationiof the sulphur dioxide controlling atmosphere, as that mustbe determined in accordance with the character of the fruit and theextent to which the same has been impregnated with sulnhur dioxide bythe grow- Lot No. 1 Lot No. 2

(a) Sweating period:

Initial temperature ..9... 105 F. 107 F Temperature maintained 123. 136.Time 48hours. 6 hours (b) Circulating period-2 v Temperature maintained123 F. 138 F ime 48 hours. 6 hours We preferably employ a moist sulphurcontrolling atmosphere toavoid too rapid drying of the fruit, as we findthat by maintaining.

the wettedcondition of the fruit the latter is rendered more readilysusceptible to the action of the sulphur controlling atmosphere. Forthis purpose we preferably introduce and condense steam into the chamber'7 during the maintenance of the fruit therein subject to the sulphurcontrolling atmosphere. We also preferably maintain the chamber 7 at anelevated' t emperature during the conversion of the sulphur dioxidecontent of the fruit by the sulphur controlling atmosphere, as we findthe latter action more readily proceeds at elevated temperatures.

Our invention is not limited to the details above specified, and thedescription here contained is for purposes of illustration only. Ourinvention is of the fullscope set forth in the following claims.

We claim:

1. The process of treating previously sulphured dried fruit to controlits sulphur dioxide content comprising subjecting the fruit to theaction of air at an elevated temperature in the resence of moisture. y

2. T e" process of treating previously sulphured dried fruit to controlits sulphur dioxide content comprising washing the fruit with water' andsubjecting the wetted fruit to .to the-action of air at an elevatedtemperature.

3. The rocess of treating previously sulphured dried fruit to controlits sulphur dioxide content comprising wetting the fruit above 110 tosweat the fruit, and then subjecting the fruit to the action of air atan ele vated temperature in the presence of moisture. 4. The process oftreating sulphured fruit whichcomprlses softening the fruit with water,draining excess water from the fruit, and

with heated water, maintaining the wetted fruit ina closed chamber at atemperature heating the fruit in a. closed chamber having 9 anatmosphere of high humidity.

5. The process of treating sulphured fruit which comprises exposing thefruit to the action of a moist atmosphere having a temperature in excessof the usual atmos heric temperature until suflicient sulphur dloxidehas been removed from the fruit, and cooling the fruit to normalatmospheric tempera ture. Signed this 29 day of April, 1925.

FRANCIS J. PROWSE. RAYMOND D. ROBINSON. ERNEST M. HALL. CHARLES F.FLEMINGQ

